Synthesis of metal oxide nanostructures and their applications as lithium ion battery anodes

S
YNTHESIS OF METAL OXIDE NANOSTRUCTURES AND THEIR
APPLICATIONS AS LITHIUM ION BATTERY ANODES







C
HEN YU
(B.
ENG., HONS.), NUS




A
THESIS SUBMITTED
F
OR THE DEGREE OF DOCTOR OF PHILOSOPHY (PH.D)
D
EPARTMENT OF MATERIALS SCIENCE AND ENGINEERING
N
ATIONAL UNIVERSITY OF SINGAPORE
2013

i

DECLARATION
I hereby declare that this thesis is my original work and it has been written by me in
its entirety. I have duly acknowledged all the sources of information which has been
used in this thesis.
This thesis has also not been submitted for any degree in any university previously.





__________________
Chen Yu
3
rd
Sep 2013

ii

LIST OF PUBLICATIONS
The Majority of this thesis work has been published in various international
journals and international conference:
Journal paper:
1. Y. Chen
2.
, B. Song, R. M. Chen, L. Lu and J. M. Xue, A Study of Superior
Electrochemical Performances of 3 nm SnO
2
Nanoparticles Supported by
Graphene, Journal of Materials Chemistry A, DOI: DOI:10.1039/C3TA14745B

(2014).
Y. Chen
3.
, B. Song, X. Tang, L. Lu and J. M. Xue, Ultra-Small Fe
3
O
4
Nanoparticle
/MoS
2
Nanosheet Composites with Superior Performances for Lithium Ion
Batteries, Small, DOI: 10.1002/smll.201302879 (2014).
Y. Chen
4.
, B. Song, L. Lu and J. M. Xue, Fe
3
O
4
Nanoparticles Embedded in
Uniform Mesoporous Carbon Spheres for Superior High Rate Battery Application,
Advanced Functional Materials, 24, 319-326 (2014).
Y. Chen
5.
, B. Song, L. Lu and J. M. Xue, Ultra-small Fe
3
O
4
Nanoparticle
Decorated Graphene Nanosheets with Superior Cyclic Performance and Rate
Capability, Nanoscale, 5, 6797-6803 (2013).

Y. Chen, B. Song, L. Lu and J. M. Xue, Synthesis of Carbon Coated
iii

Fe
3
O
4
/SnO
2
Composite Beads and Their Application as Anodes for Lithium Ion
Batteries, Materials Technology: Advanced Performance Materials, 28,
254-259 (2013). Invited paper
6. Y. Chen
7.
, B. Song, X. Tang, L. Lu and J. M. Xue, One-step Synthesis of Hollow
Porous Fe
3
O
4
Beads-Reduced Graphene Oxide Composites with Superior Battery
Performance, Journal of Materials Chemistry, 22, 17656-17662 (2012). (Most
Read Articles in Jul. 2012: No. 3)
Y. Chen
8.
, H. Xia, L. Lu and J. M. Xue, Synthesis of Porous Hollow Fe
3
O
4
Beads
and Their Applications in Lithium Ion Batteries, Journal of Materials Chemistry,

22, 5006-5012 (2012). (Most Read Articles in Feb. 2012: No. 1)
Y. Chen
9. X. Tang, Q. Tay, Z. Chen,
, Q. Z. Huang, J. Wang, Q. Wang and J. M. Xue, Synthesis of
Monodispersed SnO
2
@C Composite Hollow Spheres for Lithium Ion Battery
Anode Applications, Journal of Materials Chemistry, 21, 17448-17453 (2011).
(Most Read Articles in Oct. 2011: No. 7)
Y. Che n

, G. K. L. Goh and J. M. Xue,
CuInZnS-Decorated Graphene Nanosheets for Highly Efficient
Visible-Light-Driven Photocatalytic Hydrogen Production, Journal of Materials
Chemistry A, 1, 6359-6365 (2013).

iv

10. X. Tang, Q. Tay, Z. Chen, Y. Chen
Conference presentation:
, G. K. L. Goh and J. M. Xue, Cu–In–Zn–S
Nanoporous Spheres for Highly Efficient Visible-Light-Driven Photocatalytic
Hydrogen Evolution, New Journal of Chemistry, 37, 1878-1882 (2013).
Y. Chen, B. Song, L. Lu and J. M. Xue, Fe
3
O
4
/Graphene Composite for Advanced
Lithium Ion Battery Anode Application, 2013 MRS Spring Meeting, April 1-5, 2013,
San Francisco, California, USA (Oral Presentation by Y. Chen).

v

ACKNOWLEDGEMENTS
First of all, I would like to give my deepest gratitude to Dr. Xue Junmin. He
supervised my FYP study, and encouraged me to pursue higher degrees. He was more
than a teacher to me since then. I deeply appreciate his supervision, guidance, advice,
and encouragement throughout my Ph.D study. His knowledge, expertise, and
scientific attitude are the foundation for this work. It is a great honor of mine to carry
out my Ph.D study under his supervision.
In addition, I would like to express my sincere gratitude to Prof. John Wang. I
thank him for giving me the chance to carry out Ph.D study in this department. His
trust in me has been a great motivation for my graduate study.
Also, I wish to express my great appreciation to Prof. Lu Li and Mr. Song
Bohang from department of Mechanical Engineering. Their knowledge and efforts on
electrochemical measurements make the completion of this work possible.
Besides, I extend my thanks to my labmates, Dr. Eugene Choo, Dr. Sheng Yang,
Dr. Yuan Jiaquan, Dr. Tang Xiaosheng, Mr. Li Meng, Mr. Erwin, Mr. Vincent Lee, Ms.
Wang Fenghe, and Dr. Leng Mei for their cooperation and discussion. My thanks also
go to all lab technologists in my department for their coordination and assistance.
Finally, I would like to give my appreciation to my family for their
encouragements, supports, and understandings that help to complete this thesis work.
vi

TABLE OF CONTENTS
Declaration i
List of Publications ii
Acknowledgements v
Table of Contents vi
Summary x
List of Figures xii

List of Abbreviations xix
CHAPTER 1: Introduction 1
1.1 Overview of Lithium Ion Batteries 1
1.1.1 Principle of Operation 3
1.1.2 Current Status and Challenges 4
1.2 Anode Materials of Lithium Ion Batteries 6
1.2.1 Intercalation based anodes 8
1.2.2 Alloying based anodes 9
1.3.3 Conversion reaction based anodes 11
1.3 Literature Review of Metal Oxide Anode Materials 12
1.3.1 Overview 12
1.3.2 Tin Oxides as Anode Materials 13
1.3.3 Iron Oxides as Anode Materials 14
1.3.4 Strategies to Enhance Electrochemical Performances of Metal Oxides
15
1.4 Project Motivations and Designs 22
1.5 Research Objectives 25
1.6 Thesis Outline 25
CHAPTER 2: Experimental 27
2.1 Materials 27
2.2 Materials Synthesis 28
2.3 Characterizations 28
2.3.1 Morphological Study 28
2.3.2 Chemical Analysis 29
vii

2.3.3 Thermogravimetric Analysis 30
2.3.4 Electrochemical Measurements 30
CHAPTER 3: Carbon Coated Hollow SnO
2

Beads with Enhanced Cyclic
Stabilities 31
3.1 Motivations and Design of Experiment 31
3.2 Synthesis of Carbon Coated Tin oxide (SnO
2
@C) Hollow Spheres 34
3.2.1 Synthesis of PVP-Modified Polystyrene (PS) Beads 34
3.2.2 Synthesis of Tin Oxide coated Polystyrene (PS@SnO
2
) Beads 34
3.2.3 Synthesis of Tin Oxide hollow spheres 35
3.2.4 Synthesis of Carbon coated Tin oxide (SnO
2
@C) Hollow Spheres 35
3.2.5 Electrochemical Measurements for SnO
2
@C 35
3.3 Preparation Scheme of SnO
2
@C Beads 36
3.4 Characterizations of Carbon Coated Hollow SnO
2
Beads 37
3.5 Effect of Carbon Coating on Structural Integrities 41
3.6 Electrochemical Analysis of SnO
2
@C 43
3.7 Remarks 46
CHAPTER 4: Carbon Coated Porous Hollow Fe
3

O
4
Beads with Improved Cyclic
Stabilities 47
4.1 Motivations and Design of Experiment 47
4.2 Synthesis of Carbon Coated Porous Hollow Fe
3
O
4
beads (Fe
3
O
4
/C) 48
4.2.1 Preparation of Porous Hollow Magnetite (Fe
3
O
4
) Beads 48
4.2.2 Preparation of Carbon Coated Magnetite (Fe
3
O
4
/C) Beads 49
4.2.3 Electrochemical Measurements for Fe
3
O
4
/C 49
4.3 Morphological Characterization of Porous Hollow Fe

3
O
4
Beads 50
4.4 Formation Mechanism of Porous Hollow Fe
3
O
4
Beads 52
4.4.1 Morphological Characterization of Porous Hollow Fe
3
O
4
Beads at
Different Reaction Stages 52
4.4.2 Magnetic Reponses of Porous Hollow Fe
3
O
4
Beads at Different
Reaction Stages 55
4.4.3 Schematic Illustration of Porous Hollow Fe
3
O
4
Beads Formation 56
4.5 Characterizations of Carbon Coating 57
4.5.1 Morphological Characterizations 57
4.5.2 Chemical Analysis 59
4.6 Synthesis of Porous Hollow α-Fe

2
O
3
Beads 60
4.7 Electrochemical Performances of Carbon Coated Porous Hollow Fe
3
O
4
Beads
viii

61
4.8 Morphological Changes After Cycling 65
4.9 Remarks 66
CHAPTER 5: Hollow Porous Fe
3
O
4
Beads/reduced Graphene Oxide Composites
with Superior Capacity Retention Properties 68
5.1 Motivations and Design of Experiment 68
5.2 Synthesis of rGO Incorporated Porous Hollow Fe
3
O
4
Beads (Fe
3
O
4
/rGO) 70

5.2.1 Preparation of GO 70
5.2.2 Synthesis of rGO Incorporated Porous Hollow Fe
3
O
4
Beads
(Fe
3
O
4
/rGO) 70
5.2.3 Synthesis of rGO 71
5.2.4 Electrochemical Measurements for Fe
3
O
4
/rGO 71
5.3 Morphological Characterization of Fe
3
O
4
/rGO 72
5.4 Synthesis Mechanism 74
5.5 Characterizations of GO and rGO 75
5.6 Chemical and Porosity Characterization of Fe
3
O
4
/rGO 77
5.7 Electrochemical Performances of Fe

3
O
4
/rGO 80
5.8 Remarks 87
CHAPTER 6: Fe
3
O
4
nanoparticles embedded in uniform mesoporous carbon
spheres for superior high rate battery applications 88
6.1 Motivation and Design of Experiment 88
6.2 Synthesis of Uniform Mesoporous Carbon Spheres embedded by Fe
3
O
4

Nanoparticles (IONP@mC) 90
6.2.1 Synthesis of Water-soluble Fe
3
O
4
Nanoparitlces (IONP) 90
6.2.2 Synthesis of Iron Oxide Nanoparticles Embedded in Polymeric
Composite (IONP@PC) 90
6.2.3 Synthesis of Iron Oxide Nanoparticles Embededd in Mesoporous
Carbon Beads (IONP@mC) 91
6.2.4 Electrochemical Measurements for IONP@mC 91
6.3 Synthesis Scheme 92
6.4 Morphological Characterizations 95

6.5 Porosity Characterizations 100
6.6 Chemical Analysis 103
ix

6.7 Electrochemical Characterizations 104
6.7.1 Electrochemical Performances of IONP/mC 104
6.7.2 Comparison with other reported Fe
3
O
4
/G Anodes 110
6.7.3 Morphological Effect on the battery performances of IONP@mC 111
6.7.4 Effect of IONP Percentage on Electrochemical Performances of
IONP@mC 112
6.7.5 Effect of Carbonization Temperature on the Electrochemical
Performances of IONP@mC 113
6.7.6 Morphological Characterizations of IONP@mC after Electrochemical
Tests 116
6.8 Remarks 118
CHAPTER 7: Ultra-small Fe
3
O
4
nanoparticles-decorated graphenes with
superior cyclic performance and rate capability 120
7.1 Motivation and Design of Experiment 120
7.2 Synthesis of Ultra-small Fe
3
O
4

nanoparticles decorated graphenes (USIO/G)
123
7.2.1 Preparation of GO 123
7.2.2 Synthesis of Ultra-small Fe
3
O
4
nanoparticles decorated graphenes
(USIO/G) 123
7.2.3 Electrochemical Measurements for USIO/G 124
7.3 Synthesis Scheme 124
7.4 Characterization of USIO/G 125
7.5 Chemical Analysis 130
7.6 Porosity Characterization of USIO/G 132
7.7 Electrochemical Performances of USIO/G 133
7.8 Remarks 140
CHAPTER 8: Conclusions and Recommendations for Future Works 141
8.1 Project Conclusions 141
8.2 Recommendations for Future Works 148
8.2.1 Ultra-Small Tin Oxide and Graphene Composite 148
8.2.2 Synergistic Effect between Iron Oxide and Tin Oxide 150
Bibliography 154


x

SUMMARY
Lithium ion batteries (LIBs) have been extensively studied owing to their
growing importance as one of the major power sources for various commonly used
applications, ranging from portable electronics to electrical automobiles. Anode, as

one of the crucial components of a LIB, controls every aspect of the performance for a
LIB. Graphite, developed back in 1991 by SONY, still dominate the anode market due
to its relative stable performance, low cost and safety. However, to meet the fast
developing technologies, the performances of graphite, especially in term of capacity
(with a theoretical value of 372 mAh g
-1
), must be greatly enhanced.
Metal oxides, as potential LIB anode materials, have attracted great interest in
both scientific and industrial fields due to their much higher theoretical capacities than
that of graphite. In this thesis, two metal oxides, namely tin oxide (SnO
2
) and iron
oxide (Fe
3
O
4
), are studied as the active components for LIB anodes. Based on
alloying and conversion reaction mechanisms, SnO
2
and Fe
3
O
4
are able to deliver
theoretical capacities of 790 and 922 mAh g
-1
, respectively. However, due to their
intrinsic limitation of large volume changes during the lithium ion intake/release, the
electrodes consisting only metal oxides experience extremely fast fading in capacities
due to the breakdown of electron pathways within electrodes. Therefore, one focus of

this thesis is to enhance the cycle stability of metal oxide based electrodes without
compromising their high theoretical capacities too much. Besides, in order to meet
xi

current and emerging technologies with fast charging/discharge abilities, the other
focus of this thesis is to enhance the rate capability of metal oxides containing anodes.
The solutions proposed in this thesis are: (1) to reduce the active metal oxides to
nano-size to better accommodate the volume changes of metal oxides and improve the
rate of lithium insertion/removal; (2) to synthesize metal oxides possessing specially
designed morphologies to alleviate the negative effect originating from the volume
changes; (3) to incorporate carbonaceous materials to enhance the electrode
conductivities, further buffering the volume change of metal oxides, and providing
additional lithium storage sites. Thus, enhanced electrochemical performances, in
terms of reversible capacity, rate capability, and cyclic stability, are expected.
This thesis contains five parts to elaborate the synthesis and performances of
various metal oxides based anodes. The first two parts focus on the synthesis of SnO
2

and Fe
3
O
4
combined with glucose-derived carbon, respectively, with the major
purpose to deliver higher stable reversible capacities over that of graphite. The third
part presents the study on the incorporation of reduced graphene oxide (rGO) into
Fe
3
O
4
beads, showing extremely satisfactory cycling performance. The fourth part

introduces the concept of ultra-small Fe
3
O
4
(USIO) particles. By embedding them in
ordered mesoporous carbon beads, the composite electrode demonstrated superior
high rate performances. The firth part combines the USIO particles with rGO
demonstrating satisfactory performances in all three terms of capacity, rate capability,
and cyclic stability.

xii

LIST OF FIGURES
Figure 1-1: Comparison of different battery technologies in terms of volumetric and
gravimetric energy densities.
[6]
3
Figure 1-2: Schematic representation of the operation principles of a LIB. 4
Figure 1-3: Changes of 18650 LIB cells production over years.
[9]
5
Figure 1-4: Morphology change of an electrode consisting of SnO
2
nanoparticles (A)
before and (B) after the 50 cycles.
[49]
11
Figure 1-5: Schematic representation of (A) graphene and (B) graphene oxide
structures. 21
Figure 3-1: Schematic representation of the preparation of SnO

2
@C hollow spheres
through a template-assisted method: (A) PVP-modified PS beads; (B) PS@SnO
2

beads; (C) PS@SnO
2
@GCP composite beads; and (D) SnO
2
@C hollow spheres. 37
Figure 3-2: SEM images of the as-synthesized (A) PS beads, (B) PS@SnO
2
core/shell
composite beads, (C) PS@SnO
2
@GCP composite beads, and (D) SnO
2
@C hollow
spheres. 38
Figure 3-3: (A, and B) TEM images, (C, and D) HRTEM images, (E) SAED, (F) EDX
data, (G) XRD Pattern, and (H) Raman Spectra of as-synthesized SnO
2
@C hollow
spheres. (Inset of H) Digital picture of SnO
2
hollow spheres (light yellow) and
SnO
2
@C hollow sphere (black) solutions. 40
Figure 3-4: SEM images of (A) SnO

2
hollow spheres. (B) SnO
2
and (C) SnO
2
@C
hollow spheres after store in ethanol at room temperature for one month. (D) TGA
curve of SnO
2
@C hollow spheres. 42
Figure3-5: (A) Cyclic voltammograms for SnO
2
@C hollow spheres showing the first
two cycles between 3 V and 5 mV at a scan rate of 0.05 mV s
-1
. (B) Discharge and
charge capacity (lithium storage) vs. cycle number between 2V and 5mV, (I) SnO
2
@C
hollow spheres with a current of 100 mA g
-1
(solid and hollow triangle), (II) SnO
2
@C
hollow spheres with a current of 500 mA g
-1
(solid and hollow diamond), (III) SnO
2

xiii

hollow spheres with a current of 100mA g
-1
(hollow square and cross). The dash line
is the theoretic capacity of graphite. 44
Figure 4-1: (A, B) SEM images of the as-prepared Fe
3
O
4
beads. Inset of A: the
diameter distribution of the as-prepared Fe
3
O
4
beads. (C, D) TEM images of the
as-prepared Fe
3
O
4
beads. (E) HRTEM of the highlighted region in D. (F) SAED
pattern of the as-prepared Fe
3
O
4
beads. 51
Figure 4-2: SEM images of the products collected at different intervals: (A) 5 hours,
(B) 9 hour, (C) 19 hours, (D) 1 day, (E and its inset) 2 days, and (F and its inset) 4
days. All scale bars (including the one in insets) are 200 nm. (G) Corresponding XRD
patterns of the products collected at different intervals. Dash lines correspond to the
standard peaks’ position of cubic magnetite structure. Solid line shows the

characteristic peak of Fe
2
O
3
H
2
O phase. 54
Figure 4-3: Digital images of products in ethanol obtained at different reaction
intervals (A) without and (B) with a magnetic field. 55
Figure 4-4: Schematic representation of the formation of porous hollow Fe
3
O
4
beads.
Purple and yellow particles correspond to Fe
2
O
3
and Fe
3
O
4
phase, respectively. 56
Figure 4-5: (A and its inset) SEM images of Fe
3
O
4
/C beads. Scale bar of inset: 200
nm. (B) TEM images of a Fe
3

O
4
/C bead. Inset: magnified surface morphology of
Fe
3
O
4
/C bead. Scale bar of inset: 20 nm. (C) TGA curves of the as-obtained Fe
3
O
4

and Fe
3
O
4
/C beads. 57
Figure 4-6: TEM image of the surface of a bare Fe
3
O
4
bead. 59
Figure 4-7: XPS spectra of (A) C 1s, (B) O 1s and (C) Fe 2p of bare Fe
3
O
4
beads 60
Figure 4-8: (A, B) SEM images and (C) corresponding XRD pattern of the
as-obtained 𝛂-Fe
2

O
3
beads. 61
Figure 4-9: (A) The discharge/charge profiles of Fe
3
O
4
/C composite beads at a current
density of 100 mA g
-1
. (B) Discharge and charge capacity (lithium storage) vs. cycle
number between 3V and 5mV, (I) Fe
3
O
4
/C composite beads with a current density of
100 mA g
-1
(solid and hollow triangles), (II) Fe
3
O
4
/C composite beads with a current
density of 500 mA g
-1
(solid and hollow squares), (III) hollow Fe
3
O
4
beads with a

xiv

current density of 100 mA g
-1
(solid and hollow spheres), (IV) bare Fe
2
O
3
beads with
a current density of 100 mA g
-1
(solid and hollow diamonds), (V) solid Fe
3
O
4
beads
with a current density of 100 mA g
-1
(solid and hollow dots). The dash line is the
theoretic capacity of graphite. 63
Figure 4-10: (A) The typical morphology of a broken Fe
3
O
4
bead and (B) an intact
Fe
3
O
4
/C bead found after 50 cycles of charging/discharging. 66

Figure 5-1: (A) Low magnification and (B) high magnification SEM images of the
as-obtained Fe
3
O
4
/rGO composites. SEM images of typical (C and its inset)
half-spherical and (D and its inset) spherical Fe
3
O
4
beads. Scale of insets: 200 nm. (E)
Low magnification TEM image of a single Fe
3
O
4
bead on rGO sheet. Inset: high
magnification TEM image of the highlighted region in E. Scale of inset: 2 nm. (F)
XRD pattern of Fe
3
O
4
/rGO composite. Inset: magnified (002) peak originated from
rGO sheets. 73
Figure 5-2: Schematic illustration of Fe
3
O
4
/rGO composites via solvothermal route. 75
Figure 5-3: (A) Low magnification SEM image of the obtained GO sheets. (B) AFM
image of GO sheet with height profile. (C) Low magnification TEM image of rGO

sheet at the vicinity of a Fe
3
O
4
bead. (D) High magnification TEM image of the
highlighted region in C. Inset: SAED pattern of rGO sheet. 77
Figure 5-4: XPS spectra of C 1s from (A) GO and (B) Fe
3
O
4
/rGO. (C) Raman spectra
of GO (red) and Fe
3
O
4
/rGO (black). (D) Nitrogen adsorption and desorption isotherm
of Fe
3
O
4
/rGO composite. 79
Figure 5-5: (A) Discharge/charge profiles of Fe
3
O
4
/rGO composite electrode for the
first five cycles. (B) Cycling performance of Fe
3
O
4

/rGO composite beads (blue solid
and hollow spheres), and bare Fe
3
O
4
beads (red solid and hollow diamonds). (C)
Cycling performance of composite electrode obtained through mechanical mixing
Fe
3
O
4
beads and rGO sheets. (D) Cycling performance of pure rGO. Inset:
Discharge/charge profiles of rGO electrode for the first two cycles. All curves
presented in this figure were tested between 3V and 50mV with a current density of
100 mA g
-1
. 81
xv

Figure 5-6: TGA curves of the obtained Fe
3
O
4
/rGO composite. 82
Figure 5-7: SEM images of the obtained bare Fe
3
O
4
beads. 83
Figure 5-8: (A), (B) SEM images of solvothermally obtained Fe

3
O
4
/rGO composite
after cycling. (C), (D) SEM images of bare Fe
3
O
4
beads after cycling 84
Figure 5-9: SEM images of obtained Fe
3
O
4
/rGO mixture obtained by mechanical
mixing. 85
Figure 5-10: Rate capability of Fe
3
O
4
/rGO composites and (B) bare Fe
3
O
4
beads
electrodes at various current densities between 50 and 2000 mA g
-1
. 87
Figure 6-1: Schematic representation of the formation of IONP@mC-600. (A) IONPs
and F127 micelles, (B) resol-Fe
3

O
4
and resol-F127 monomicelles, (C) IONP@PC, (D)
IONP@mC, (E) cross section of IONP@mC, and (F) magnified representation of a
channel of IONP@mC. 93
Figure 6-2: (A) TEM image and (B) SAED pattern of ultra-small water-soluble
IONPs. 94
Figure 6-3: TEM images of IONP@PC (A-C) and IONP@mC-600 (D-F). Insets of B
and D: magnified TEM images of one IONP@PC and IONP@mC-600. Insets of C
and F: SAED patterns of IONP@PC and IONP@mC-600. 95
Figure 6-4: Particle size distributions of (A) IONP@PC and (B) IONP@mC-600. 96
Figure 6-5 TEM images of IONP@mC-600 with different incorporated IONPs
amount. (A, B) Mesoporous carbon spheres without IONP incorporated (mC-600). (C,
D) IONP@mC-600-1 and (E, F) IONP@mC-600-2 were two sets of samples with
increasing IONP content, both of which were lower than that of IONP@mC shown in
Figure 1D-1F. 98
Figure 6-6: (A, B) TEM images and (inset of B) SAED pattern of IONP@mC-450. . 99
Figure 6-7: XRD patterns of IONP@PC (lower black line) and IONP@mC-600
(upper red line). 100
Figure 6-8: (A) Nitrogen sorption isotherms, (B) corresponding pore size distribution
curves, and (C) Structural and textual properties of (a) mC-600, (b) IONP@mC-600,
(c) IONP@mC-450, and (d) IONP@PC. 101
xvi

Figure 6-9. TGA curves of IONP@mC-600 (red), IONP@mC-450 (blue), and
IONP@PC (green). 102
Figure 6-10: XPS spectra of (A) IONP@PC and (C) IONP@mC-600. High resolution
XPS spectra of C1s from (B) IONP@PC and (D) IONP@mC-600. 103
Figure 6-11: (A) XPS and (B) high resolution XPS spectra of C1s from
IONP@mC-450. 104

Figure 6-12: Electrochemical performances of IONP@mC-600, IONP@mC-450, and
IONP@PC. Charge/discharge profiles of IONP@mC-600 at (A) current densities of
500 mA g
-1
and (B) higher rates from 1000 to 10000 mA g
-1
. Rate capability tests of
IONP@mC-600 (blue sphere), IONP@mC-450 (red diamond), mC-600 (orange
square), and mC-450 (green triangle) (C) from 500 to 2000 mA g
-1
, and (D) from
3000 to 10000 mA g
-1
. (E) Subsequent cycling tests of IONP@mC-600 and
IONP@mC-450 at 2000 mA g
-1
for 500 cycles. 105
Figure 6-13: Comparison of the battery performances between IONP@mC and
reported Fe
3
O
4
/graphene composites at current densities above 1000 mA g
-1
.
[83, 131, 142,
145, 146, 174, 175]
110
Figure 6-14: TEM images of (A, B) IONP@PC and (C, D) IONP@mC-600 with
higher Fe

3
O
4
percentage. 112
Figure 6-15: Electrochemical performances of of IONP@mC-600 (blue sphere) and
IONP@mC-600 with higher Fe
3
O
4
percentage (orange triangle) (A) from 500 to 2000
mA g
-1
, and (B) from 3000 to 10000 mA g
-1
. 113
Figure 6-16: High resolutin XPS spectra of C1s from (A) IONP@mC-750 and (B)
IONP@mC-900. TEM image of (C) IONP@mC-750 and (D) IONP@mC-900. 114
Figure 6-17: Electrochemical performances of IONP@mC-600 (blue sphere),
IONP@mC-450 (red diamond), IONP@mC-750 (purple triangle), and
IONP@mC-900 (yellow square) (A) from 500 to 2000 mA g
-1
, and (B) from 3000 to
10000 mA g
-1
. 115
Figure 6-18: SAED patterns of IONP@mC calcinated at (A) 750
o
C and (B) 900
o
C.

115
xvii

Figure 6-19: (A, B) SEM and (C, D) TEM images of IONP@mC-600 beads after 790
cycles of charge/discharge with the current densities ranged from 500 to 10000 mA
g
-1
. 116
Figure 6-20: (A) Comparison of XRD patterns of IONP@mC-600 electrodes (on Cu
foil) before and after 1 cycle of charge/discharge. (B) X-ray diffraction pattern of
IONP@mC-600 beads after 790 cycles of charge/discharge with the current densities
ranged from 500 to 10000 mA g
-1
. 118
Figure 7-1: Schematic illustration of the formation process of USIO/G. 125
Figure 7-2: (A-D) TEM images of the as-obtained ultra-small iron oxide/graphene
(USIO/G) composites before annealing. Inset of C: SAED pattern of USIO/G. Inset of
D: high resolution TEM image of selected area in D. (E) TEM image, (inset of A)
HRTEM image, and (F) SAED pattern of annealed USIO/G composites. 126
Figure 7-3: (A) SEM image of USIO/G and the corresponding EDS mapping in the
same area with relative intensities of (B) carbon, (C) iron, and (D) oxygen. 127
Figure 7-4: Size distribution of Fe
3
O
4
particles (A) before and (B) after annealing. 129
Figure 7-5: Thermogravimetric curve of the annealed USIO/G composite. 129
Figure 7-6: XRD pattern of the annealed USIO/G composites. 130
Figure 7-7: High resolution XPS spectra of C1s from USIO/G (A) before and (B) after
annealing. 131

Figure 7-8: High resolution XPS spectrum of C1s from GO. 132
Figure 7-9: XPS spectrum of Fe2p obtained from USIO/G 132
Figure 7-10: Nitrogen adsorption and desorption isotherms of USIO/G (A) before and
(B) after annealing. 133
Figure 7-11. Charge-discharge profiles of the annealed USIO/G composite: (A) first
four cycles at a current density of 90 mA g
-1
, and (B) first cycles at various current
densities. (C) Rate capability test and (D) subsequent cyclic test of the annealed
USIO/G anode. 135
Figure 7-12: Charge-discharge profiles of the annealed USIO/G composites at first
two cycles after current density restored to 1800 mA g
-1
(corresponding to total cycle
xviii

numbers of 921
st
and 922
nd
). 137
Figure 7-13: Cycling performance of pure ultra-small iron oxide (USIO) under
different current densities. Red circle: 100 cycle under current density of 100 mA g
-1
.
Blue diamond: first 3 cycles at 50 mA g
-1
, subsequent 3 cycles at 100 mA g
-1
,

followed by 94 cycles at 500 mA g
-1
. 140
Figure 8-1: Summary of electrochemical performances for the metal
oxides/carbonaceous materials composites in this thesis. 145
Figure 8-2: Comparison of rate capability of different composites in this thesis. 147
Figure 8-3: (A) SEM image of USTO/G and the corresponding EDS mapping in the
same area with relative intensities of (B) tin, (C) carbon, and (D) oxygen. 149
Figure 8-4: (A) TEM and (B) high resolution TEM images of ultra-small USTO/G
composites. 150
Figure 8-5: SnO
2
Nanoparticles grown on hollow porous Fe
3
O
4
beads at different time
intervals: (A1) 0 h. (A2) 2 h, (A3) 5 h, and (A4) 8 h. SnO
2
nanorods grown on hollow
porous Fe
3
O
4
beads at different time intervals: (B1) 0 h, (B2) 2 h, (B3) 5 h, and (B4) 8
h. 152
Figure 8-6: (A) SEM image of USIO/USTO/G and the corresponding EDS mapping
in the same area with relative intensities of (B) carbon, (C) oxygen, (D) iron, and (E)
tin. (F) EDS spectrum with table presenting weight and atomic percentages for
different elements. 153

xix

LIST OF ABBREVIATIONS
ABCVA - 4, 4’-Azobis (4-cyanovaleric acid)
AFM – Atomic Force Microscope
BET - Brunauer-Emmett-Teller
C – Carbon
DDA – Dodecylamine
DEC - Diethyl Carbonate
DHAA –Dehydroascorbic Acid
DMC – Dimethyl Carbonate
EC - Ethylene Carbonate
EDS - Energy-dispersive spectroscopy
G – Graphene
GO - Graphene Oxide
IONP – Iron Oxide Nanoparticle
LIB - Lithium Ion Battery
mC – Mesoporous Carbon
NMP - n-Methyl-2-Pyrrolidone
PC – Polymeric Composite
PS – Polystyrene
PVDF - Polyvinylidene Fluoride
PVP - Polyvinylpyrrolidone
rGO - Reduced Graphene Oxide
SEM – Scanning Electron Microscope
xx

TEM – Transmission Electron Microscope

TGA – Thermogravimetric Aanalysis
USIO – Ultra-Small Iron Oxide
USTO – Ultra-Small Tin Oxide
XPS – X-Ray Photoelectron Spectroscope
XRD – X-Ray Diffraction


1

CHAPTER 1: INTRODUCTION
1.1 OVERVIEW OF LITHIUM ION BATTERIES
It is currently widely recognized that the green house gases, which are emitted
from traditional power sources based on combustion reactions, not only pollute the air
that shared by every living creature, but also creating a serious consequence of global
warming.
[1]
Such fact concentrates attention to the search of renewable energies as
alternative energy sources.
[2]
Nuclear reactor, which has been considered as a
promising candidate for future power source, showed its disastrous shortcoming in
recent tragedy in Fukushima nuclear plant, Japan.
[3]
As other currently available
renewable energy sources, solar radiation, geothermal energy, wind, and waves vary
in both time and space.
[4]
Therefore, batteries, as electrical energy storage devices, are
necessary to store the unstable energy deliver from all of these energy sources.
Furthermore, electrical energy, delivered directly from batteries, is readily available in

most industrial and domestic usages. Besides, compared with traditional power
sources based on combustion reaction, batteries do not have any carbon dioxide
emission which is considered as a major factor in undesirable global climate changes.
Lithium ion batteries (LIBs), as a type of secondary battery (rechargeable
battery), have attracted tremendous attention during recent years, owning to their
dominating advantages over traditional batteries.
[5]
Besides light weight, LIBs do not
suffer from any memory effect, which is the term that describes permanent loss in
2

capacity if the battery is recharged without being fully discharged. Furthermore,
compared with other rechargeable batteries, LIB has the lowest self-discharge rate.
Therefore, LIBs have already been chosen to be the power sources of various
applications, ranging from a tiny music player to a massive sport car. More
importantly, compared with other currently available battery technologies, LIBs have
outstanding performances in term of energy density.
[6]
Figure 1-1 shows the
comparison of different battery technologies in term of volumetric and gravimetric
energy densities. These two terms shown on two axes, namely electrical energies per
unit mass (Wh kg
-1
) and per unit volume (Wh L
-1
), are directly linked to the cell
capacity (Ah kg
-1
) of a functioning LIB cell. The lithium metal battery technology,
which lies at the top right corner in, has been reported to have severe safety concerns

due to the dendritic lithium growth on lithium electrode surface as the lithium
redeposit on it,
[7]
thus leaving the LIB as the available technology with highest energy
density. Unsurprisingly, LIB is now dominating the secondary battery market. For
example, in April 2013, LIBs account for over 55% of the production of all secondary
batteries in Japan.
[8]

3


Figure 1-1: Comparison of different battery technologies in terms of volumetric and
gravimetric energy densities.
[6]

1.1.1 PRINCIPLE OF OPERATION
In practical, each LIB usually consists of many electrochemical cells connecting
in parallel or in series. The electrical energies are stored within each cell in forms of
chemical energies. Through electrochemical reactions, these two forms of energies
can be converted into each other.
Figure 1-2 shows the schematic representation of the interior structures and
operation principles of a LIB. There are three major components in a typical LIB:
positive electrode (cathode), negative electrode (anode), and electrolyte that separates
the two electrodes. During a charge process, an external voltage is applied and the
lithium ions move from cathode to anode through electrolyte; meanwhile, electrons
move in the same directions through external circuit to maintain the charge balance.
During a discharge process, the two electrodes are connected to a device by an
4

external circuit.

Figure 1-2: Schematic representation of the operation principles of a LIB.
Due to the difference in electrochemical potentials between the two electrodes,
lithium ions are released by the anode and move to the cathode. Such movement is
compensated by the electron diffusion in the same direction through external circuit
passing the connecting device. Therefore, external electrical energy converts to
chemical energy when the battery is charged and converts back when the battery is
discharged. Due to the reversibility of the electrochemical reactions occurring at both
electrodes, LIBs are rechargeable. The basic criterion for the electrodes is that they
can reversibly uptake/release lithium ions; while the electrolyte should be a good
ionic conductor and also an electronic insulator.
1.1.2 CURRENT STATUS AND CHALLENGES
Owing to its unambiguous advantages over other existing battery technologies,
LIB has been recording with increasing production each year.
Figure 1-3 shows the overall capacities of the production of commonly used